1. Field of the Invention
The present invention relates to a vertical offset structure and a method for fabricating the same, and more particularly, to a vertical offset structure used for a vertical operation type capacitance electrode, and a method for fabricating the same
2. Description of the Related Art
Vertical offset structures can be manufactured using a micro electro mechanical system (MEMS). MEMS is a technology that embodies mechanical and electrical components using a semiconductor process. Examples of a system manufactured by MEMS technology include: an accelerometer for sensing acceleration of a moving object, an angular velocity meter for sensing a rotating velocity of a rotating object, and an optical switch for controlling an optical path.
Performance of a vertical offset structure using MEMS technology is determined according to whether or not an upper surface and a lower surface of the vertical offset structure form a perfect vertical offset. The performance of a vertical offset structure is further determined by the narrowness of a horizontal interval between vertical offset structures, in order to improve vertical driving and sensing performances.
FIGS. 1A to 1D are views showing a vertical offset structure using MEMS technology.
In detail, FIG. 1A is a view showing a vertical offset structure manufactured using a(bilateral arrangement of a conventional wafer. The vertical offset structure using a bilateral arrangement of a wafer is manufactured by simultaneously processing respective front and rear surfaces of the wafers after arranging two wafers in a line. In the vertical offset structure manufactured by such a method, it is difficult to obtain a horizontal interval of less than 5 μm between a movable electrode and a fixed electrode due to a bilateral arrangement error in wafers. A fixed electrode and a movable electrode manufactured by such a method cannot function as a comb electrode having overlap.
FIG. 1B is a view showing a vertical offset structure manufactured using a conventional dual mask and undercut etching characteristics.
As described above, a method as shown in FIG. 1A manufactures the vertical offset structure using a bilateral arrangement of wafers. In contrast, referring to FIG. 1B, a vertical offset structure is manufactured at one wafer using a dual mask and undercut etching. Therefore, unlike the vertical offset structure manufactured using a dual arrangement of wafers, the method of FIG. 1B may form a small horizontal interval between a movable electrode and a fixed electrode. However, as shown in FIG. 1B, when the vertical offset structure is manufactured using the dual mask and the undercut etching characteristics, the manufacturing process is significantly complicated. Further, since an electrode is manufactured using a dual mask, it is difficult to obtain a horizontal interval of less than 2 μm between a movable electrode and a fixed electrode due to an arrangement error.
FIG. 1C is a view showing a vertical offset structure manufactured using a conventional reactive ion etching (RIE) lag and undercut etching characteristics. More specifically, FIG. 1C is a perspective view showing a fixed electrode and a movable electrode of a vertical offset structure manufactured using RIE lag and undercut etching characteristics which occur due to an etching ratio difference according to a pattern size opened while a deep thin film is being etched by RIE, and a cross-sectional view thereof taken along line A—A′. Unlike the vertical offset structure of FIG. 1B, the vertical offset structure of FIG. 1C is manufactured using one mask. Accordingly, since it is possible to form a small horizontal interval between a fixed electrode and a movable electrode, a manufacturing process is relatively simple. However, as shown in an area B, since a vertical offset is formed at only a lower portion of the fixed electrode and not at an upper portion of the fixed electrode, a perfect vertical comb electrode and a vertical offset structure having the same cannot be manufactured. Therefore, when the vertical offset structure is used for a capacitance electrode, the sensitivity thereof is reduced.
FIG. 1D is a plan view showing an example of a conventional vertical offset structure.
With reference to FIG. 1D, the conventional vertical offset structure includes a movable electrode and a fixed electrode. The movable electrode is vertically moved, but the fixed electrode is not moved. The vertical offset between the movable electrode and the fixed electrode, as described by reference to FIGS. 1A to 1C, is formed during a formation of the vertical offset structure. As a result, a procedure for manufacturing the vertical offset structure becomes complicated.